I have 6 pregnant guppies. They are all about 2 - 3 months pregnant and are really fat. But everytime i put them into the hatchery their gravid spot fades away. Is this because of stress? And another question. Roughly how long do you reckon till they drop? I will try to get pics of them asap.
Poor Guppies! Poor You!!!
I find they seem to take forever to actually get down to the labouring/birthing. Just when you think they'll burst before they give birth they seem to actually do it - seems to me removing them is definately not a good idea, stress does indeed slow down the process friend.
Leave them there and if you are worried about them being eaten (and they are likely to be), keep a watchful eye and remove the fry when they are born. Don't be too concerned about that they seem very hardy to me, and put them into the "hatchery" you have in mind after. There will be some fry casualties but they will probably have so many fry from the six guppies you'll end up with way too many anyway.
Guppies don't seem very hardy while birthing either. Keep an eye on that. When in distress they tend to curl in on themselves and lie on flat leaves, rocks, sand or whatever you got in there. They can be saved with assisting their birthing, but don't interfere unless you feel you need to.
good luck, but be very, very patient

it will happen, I assure you!!!